Method of obtaining chemical resistant concrete

ABSTRACT

Disclosed herein is a method of obtaining chemical resistant concrete, the essence of the method consisting in that use is made as starting components of the concrete binder, of highsilica alkaline glass with a silica modulus in excess of 6, and quartz sand comminuted into particles with a specific surface of at least 1,000 cm2gr.

United States Patent [191 Kirilishin et al.

[ Aug. 28, 1973 [22] Filed: July 15, 1970 [21] Appl. No.: 55,232

[52] US. Cl. 106/84 [51] Int. Cl. C041) 35/14, C041) 35/16 [58] Field ofSearch 106/74, 84; 264/82 [56) References Cited UNITED STATES PATENTS3,498,802 3/1970 Bickford et al. 106/74 2,240,393 4/1941 Dietz 106/842,492,790 12/1949 Farkas et al. 106/84 2,662,022 12/1953 Dietz 106/84Primary Examiner-James E. Poer Attorney-Waters, Roditi, Schwartz &Nissen 5 7] ABSTRACT Disclosed herein is a method of obtaining chemicalresistant concrete, the essence of the method consisting in that use ismade as starting components of the concrete binder, of high-silicaalkaline glass with a silica modulus in excess of 6, and quartz sandcomminuted into particles with a specific surface of at least 1,000cmgr.

3 Claims, No Drawings METHOD OF OBTAINING CHEMCIAL RESISTANT CONCRETEThis invention relates to a method of obtaining chemical resistantconcrete for use in industrial, hydraulicengineering and undergroundconstruction of buildings and structures that are to operate underconditions in which they are subject to chemically active media,especially acid ones, as well as for use in the constructing ofheat-generation plants.

Known in the art is a method of obtaining chemical resistant concretebased on a binder whose basic components are vitreous sodium silicatesor potassium silicates with a silica modulus of less than 4.

As a result of dissolving vitreous silicate in water, soluble glass isobtained.

With the purpose of making liquid glass solidifiable and increasing itswater-proofness some additives are introduced into the composition ofthe concrete, such as sodium silicofiuoride, which additives neutralizethe alkali in liquid glass and convert it into water-insoluble compoundin the course of alkali neutralization a free silica is evolved from theliquid glass in the form of a gel which serves as a binder, i.e., itcements the particles of the concrete aggregate and, after having beendehydrated under dry conditions, imparts strength to the resultingconcrete.

Since silica! gel serves in the above case as a cementing agent such aconcrete is not attackable by most of the high-concentration mineralacids but is. likely to quickly fall apart in alkaline-reactionsolutions. Furthermore it features but low stability in water, aqueoussolutions and water-steam media which interferes with its being widelyapplied as a chemically resisting construction material.

Likewise restricted is the application of a liquid-glass based concreteas an acidproof lining material, this being due to the toxicity ofsodium silicofiuoride and its being completely permeable to agressivesolutions.

Moreover, the low heat-resistant properties of the binder trammel itsapplication in chemically resisting fireproof concretes.

It is an object of the present invention to eliminate the disadvantagesmentioned above.

It is a specific object of the present invention to provide a method ofobtaining chemical resistant concrete based upon a binder in the form ofa free silica and involving the use, as the basic binder components, ofsuch substances in amounts that make the resulting concrete chemicallyresistant to both acids and alkalis of any concentration, solutions ofsalts, as well as make the concrete absolutely waterproof, non-toxic,impart to it excellent physico-mechanical and thermal'properties and,whenever necessary, impermeability to aggressive solutions.

The above and other objects are accomplished due to the fact that forobtaining chemical resistant concrete, according to the invention, useis made as the basic binder components of high-silica alkaline glasswith a silica modulus not in excess of 6, in an amount of 20 to 60weight percent, and quartz sand comminuted into particles with aspecific surface of at least 1,000 sq.cm/gr. in an amount of 80 to 40weight percent.

The essence of the present invention resides in the following:

With the silica modulus of the liquid glass in excess of 6 the essentialquantity of vitreous silica is in a free state, not bound intosilicates. Therefore, high-silica glasses are practically insoluble inwater even at elevated temperatures and are not suitable for obtainingliquid glass.

However, when subjected to heat and wet treatment jointly with finelycomminuted quartz sand, silica glass exhibits water solubility andability to crystallize into quartz on particles of comminuted quartzsand as in innoculating crystals or seeds.

This is explained by the fact that the solubility of vitreous silica inwater under similar conditions is considerably higher than that ofquartz (crystalline silica). Therefore, a silica solution in the make-upwater that occurs, in order to be saturated with respect to glass, willbe supersaturated with respect to quartz.

This fact is responsible for a spontaneous deposition (crystallization)of excess silica on quartz particles in the form of quartz occurring inthe course of heat and wet treatment.

Besides, an additional amount of silica is passed into the solutiondepleted in silica from high-silica glass, whereupon the whole processis repeated until a complete dissolution of glass and itscrystallization on the particles of finely comminuted quartz sand occur.

Growth of quartz particles due to dissolution and crystallization ofhigh-silica glass results in the particles being intergrown along thecontact surfaces, i.e., in solidifying of the binder and concrete.

Thus, in the present invention, use is made as a binder of unfixedsilica not in the form of gel but as a more thermodynamically andchemically stable crystalline variety of unbound silica, that is,quartz. This is a decisive factor in the obtaining of excellentchemical, physical, thermal and mechanical characteristics of the binderand the chemical resistant concrete based thereon.

The spirit of this invention will be better understood from aconsideration of specific exemplary embodiments of the method disclosedherein.

To obtain chemical resistant concrete, there were used: high-silicaglass with a silica modulus of 9.3 of the following weight percentagecomposition: Si0,-; Na- ,O-lO, in the form ofgrains ofa size of 0.6 toI25 mm; finely dispersed high-silica glass and quartz sand comminutedinto particles with a specific surface of 3,000 sq.cmlgr as an additive;and fine quartz sand with a size modulus of 1.15 as an aggregate.

The above-listed components were intermixed in a concrete mixer, waterwas added, whereupon the mixture was agitated until a homogeneousconcrete mass was obtained.

The following amount of constituents were used to obtain I cum. ofconcrete mass (in kg):

high-silica glass (in grains)350 high-silica glass (ground)50 sandaggregate-1120 sand additive-400 water-225 Utilization in the aboveexample of granulated glass with a grain size of 0.6 to 1.25 mm andquartz sand as an aggregate made it possible to cardinally decrease theoriginal surface area of the binder and thereby to obtain a concretemixture with a minimum water-binder ratio and higher concrete densitycompared to concrete based upon finely comminuted glass.

From the concrete mixture thus obtained there were shaped rectangularspecimens measuring 4X4Xl6 cm and and figure-eight specimens which werethen subjected to autoclave precessing at 190 C. After having beendried, the concrete showed the following charac- 5 teristics:

ultimate strength, kg/cm:

compression470.2-6l 1 .0 bending136.ll46.7 tensile62.l-

iO hancing the reliability and service life thereof.

Concrete mixture composition, kgJlit.

Characteristics of concrete Comminuted Chemical resistance, High silicasodium glass quartz sand Sand aggregate Strength, Ina/cm." percentminimum Specific Acid Alkali Silk-n Groin surince, Sill. MainCmnprnsresistance resistance Nos modulus Quantity size, mu. Quantitycmfi/gr. Quantity modulus water siun landing at 111 12 at ill :1

2 7. 5 0. ii 140-316 0. 4 5,800 0.1! 2. 2i 0. 71!). 5 M'J. 8 JO. 0 J7.0.0 0.35 50 0.4 6,800 1.2 1.16 0.211 214.1 48.2 90.0 96.5 7.5 0.4315-030 01.4 1,100 0.28 427.5 102.0 99.0 97.8

High silica potassium glass ing comminuted concrete during 1 hour,percent:

a. in a -percent solution of sodium hydroxide8i.56

b. in a solution of sodium hydroxide at 10' moi/lit.

concentration and pH l298.43

Fire-proofness of the concrete with sand aggregate 35 precaicined atl,200C to convert quartz into tridymite, C.l,670

The production technique described above is instrumental in obtainingchemically resisting concrete of 40 other compositions. Given below is atable containing data on concrete composition and properties.

Due to its high chemical, physical and mechanical characteristics,concrete obtainable by the hereindisclosed method can find widespreadapplication in What is claimed is:

- l. A method of preparing chemical resistant concrete comprising mixingalkali high-silica glass having silica modulus of more than 6 and quartzsand comminuted to a specific surface area of at least 1,000 cmlg, saidglass being present in an amount of 20-60 wt.% and said sand in anamount of 4080 wt.%; adding water to the resulting mixture, andrepeating the mixing step until a uniform plastic mixture is obtained;molding the desired articles from said uniform plastic mixture; andsubjecting the resulting molded articles to autoclave treatment for aperiod of time sufficient for causing said glass to dissolve completelyand for allowing the quartz to crystallize out of the solution onto thesurface of particles of said quartz sand.

2. A method as claimed in claim 1, comprising adding quartz sand as afiller into said resulting mixture to gether with said water.

3. A method as claimed in claim 1 wherein the alkali high-silica glasshas a grain size in the range of 140-to l,250-microns and the autoclavetreatment is conducted at a temperature of 190C. i 0 0 i

2. A method as claimed in claim 1, comprising adding quartz sand as afiller into said resulting mixture together with said water.
 3. A methodas claimed in claim 1 wherein the alkali high-silica glass has a grainsize in the range of 140-to 1,250-microns and the autoclave treatment isconducted at a temperature of 190*C.